Comment on yet another wood case design

[Gorsnak]

My current case (low end design scarcely above beige box level) has lousy airflow, and I've been lusting after that passive Gigabyte 6800 gpu. I'm also long past ready to take a big step forward in quieting my computer, which is currently much better than stock but still nothing close to silent. So, I've pretty much decided to build a case to match my desk, which I also made. It will be of the same stained pine construction. My initial model looks like this:


I realize that this is a relatively conventional design which doesn't really exploit the possibility of building something of a completely different shape, but given where it will be sitting, something roughly tower-shaped is preferable.

The psu sits in the bottom rear, and I will likely procure a Seasonic of some sort. I am undecided between the Super Silencer, which draws air from the front, and the Super Tornado, which would draw through a hole cut in the bottom of the case. Main intake is through large openings in the bottom of the case, which will stand 1.5" off the floor. This allows for large unobstructed intake space without opening up an escape route for any sound, which will tend to be absorbed by the carpet. The HD is suspended on edge over the intake, with room to add another beside it. The hsf is an Arctic Cooling Copper Silent 2 on an AMD 2100, but the design leaves clearance room above the mobo for largish upgrades of the Zalman flower sort. Exhaust is a single 120mm fan at the top rear. The optical drives will live behind a door which will also cover the power and reset switches, power and drive activity leds, and front usb ports.

The piece de resistance will be an acoustical absorbing panel (upholstered 1" fiberglass of the sort one sees hanging in auditoriums and the like) covering the inside of the door, which will be hinged at the back. Depending on sound levels, I may cover parts of the inside of the front and top as well. We make these panels at work, and I can whip little stuff like this up from scraps. It should make a large difference, particularly in the high frequencies.

Questions:

Is the intake on the bottom going to pose a problem due to the relatively limited area beneath the unit that air can be sucked from?

Is a single 120mm fan sufficient? (Probably a Nexus, since NCIX is carrying them now.) I could increase the case size a bit and stuff another one up there.

Am I likely to need to add a fan aimed at the passive Gigabyte card? (Or should I save some money and go with an MSI 6600GT modded with a ~7v L1A?)

Any idea whether a bottom-sucking PSU like the Tornado would be better or worse than a front-sucker like the Silencer?

Thanks in advance for all advice.

[GameManK]

my friend built a wooden computer and i have to tell you the wood reverberates a lot. Be sure to isolate the fans well from the case.

I like the whole bottom intake thing in your design.

[frankgehry]

Its a lot more interesting to see someone construct a case than to try new ideas in a standard case, but anyway,

- it looks like there is plenty of room below the floor of your case for the psu intake, but since the only dimension that exists is in your cad program you'll always have the opportunity to change this if needed. You need a good filter.

- One fan should be enough especially since it is high and should create a good flow pattern from bottom to top. I like the way the psu exhaust is set back from the rear surface of the case so that there is not a direct path to a sound source. I would try to do the same with the top exhaust fan and pull the fan location back from the surface so you can create a baffle to eliminate direct paths to a noise source. As it is, noise from the cpu fan would also escape.

I'm not really sure what the best way to cool the graphics card would be.

As far as the best type of psu the bottom sucker would be my choice. Again, the fan noise would be directed down towards the floor and essentially, the psu is only drawing in air too cool itself and exhausting it.

- And also, I guess wood may resonate, I really don't know, but it might be worth considering particle board with veneer, similar to speaker enclosures that are supposed to be acoustically dead. my 2 cents - FG

[Gorsnak]

I am planning on recessing the case fan in a fashion similar to the psu, I just haven't drawn that in yet. I need to model the mobo and hsf better first so I can see what the clearances are, but the idea is to stack a couple layers of wood on the inside of that hole - maybe 3 in total, for a depth of 2.25", but we'll see.

Some experimentation with a 92mm M1A and a 9v adaptor on my desktop does indeed suggest that resonance could be an issue. I hadn't really thought it would be, but clearly some thought on this matter is merited. I don't think moving to particle board would help at all, and it would look ugly. The whole point is to have it match the desk. I'm thinking more along the lines of gluing a layer of cork to the inside and making sure most everything has isolated mounts.

[frankgehry]

If the psu is sucking in air will it draw air from inside the case through the vents near the hard drive? Put a partition below the case floor separating the psu intake from the computer case intake so air will come in from the front, by the hard drives, and out the top. We want the psu to just grab air from outside the case. - FG

I'm sure you will ge a lot of help on this. Your drawings are clear and its easy to speculate about what this could be. You certainly have the craftsmanship to make something really great.

[Gorsnak]

If the psu is sucking in air will it draw air from inside the case through the vents near the hard drive? Put a partition below the case floor separating the psu intake from the computer case intake so air will come in from the front, by the hard drives, and out the top. We want the psu to just grab air from outside the case. - FG

You mean so that the psu sucks air from underneath and back, while the main intake sucks from underneath and forward? You think that's necessary? I mean, it would be easy to do, but I'd think the chance of it messing up the main intake isn't very substantial, and forcing it to suck from the back might lead to some intake of its own exhaust.

Another option would be to cut out the bottom sides, so as to make 4 individual feet. That would allow the intakes to suck from all directions, but it would still make for indirect sound paths, especially since it will be sitting on carpet. On a hard floor, the sound might bounce through, but the carpet will absorb most frequencies.

Here's a gratuitous picture of the desk so that it becomes clear why I'm looking to match it.

[frankgehry]

Oh - you're right. Drawing air from near the exhaust would be worse than the problem I was thinking about. I believe I've seen some airflow calculations somewhere on this site that would allow you to match airflow from a fan to a particular size opening. I think its just a matter of finding the fan cfm and calculating the the opening size, but its beyond me at this point, but that would answer your first question and help you decide about opening the sides of the base up. If I can find a link I'll post it for you.

[De Sjelle]

It looks like your desk is made of real wood, are you going to make the tower also in massive wood? Because you need to consider that the temps in your case are going to vary a lot... And wood needs room to move under different temps.

[teejay]

This is an interesting thread with some good ideas. I hope the actual projects gets done at some point so you can share some real-world experiences. Some ideas that come to mind in no particular order:

• Have you considered separating the psu section from the mainboard section with a wooden divider? The reason I ask is that a psu tends to radiate heat into the case interior and the wood would block this, at least to some extent;
• I'd make sure the design allows for a 120mm intake fan under the harddisk position. That way, if you decide you need it somewhere down the road you don't have to mod your case. I know that Bluefront made a case with an airflow pattern something like this and he decided to add a hdd fan at a later date;
• I'd make the intake area as large as possible without compromising case integrity. That way, you can add filtering much easier if dust should become a problem;
• If you recess the case fan in the same way as the psu, you run the risk of creating a pocket of (hot) air below it. You could install it at an angle to the back & top plane, say 30 degrees tilted with the bottom of the fan touching the back panel;
• I'd try to keep the sides in one piece without opening the sides if at all possible; that way there is less chance of noise leakage and a predictable airflow pattern. I do think you need to raise it enough, preferably so the "open" area would have the same surface area as the fan blades of a 120mm fan (87mm sq according to the Antec 3000B review on the main side). If the opening is about 15cm wide this would mean a height of ~6cm (a bit less than 2.5 inches);
• De Sjelle has a good point; I have read several stories of peoples wooden cases cracking because of rigid construction;
• One fan should be enough as long as you also have a cpu fan. If you decide to duct a tower heatsink to an outtake fan I'd start considering adding another one. Why not make your top panel interchangable so you can change the design later?

A fan that hits your passive graphics card is probably a good idea. If you can fit it you might want to try another angled 120 or 92mm fan. With the angled fan at the top this will evacuate the heat neatly and efficiently.

[alleycat]

Looks good! I wish I had a workshop (and skills!) to try ideas like these. It may sound a bit obvious, but I calculate the area of the fan using pi*r^2 and use that as a guideline for sizing the intakes. At least it gives you a ballpark figure. So according to your drawing you have approx 35mm*150mm*2 ends. That is almost the same area as a 120mm fan. You'll have two Nexus fans, and they won't be moving anywhere near the amount of air that most 120mm fans do, so I would be surprised if you ran into problems.

[teejay]

Yeah, but there are 2 fans sucking from the bottom intake (psu and case fan), so I came up with approx. twice that size. I took the 87mm square from the Antec 3000B review since MikeC substracted the fan hub size from the pi*r^2 figure. I do think this is mostly an empirical point though; Gorsnak is not likely to run into problems due to cramped intakes.

[frankgehry]

Volume/Velocity Calculations

FPM = Feet per Minute (velocity)
CFM = Cubic Feet per Minute (volume)
AREA = CFM/FPM

Assume Fan ~ 30 CFM
Area of openings = 1.5" * 7.5" * 2 = 22.5 square inches or 22.5/144 = 0.16 SF

0.16 SF = 30CFM/FPM FPM = 30/0.16 = 187.5 FPM

FPM = 187.5 FPM

Now Calculate FPM with area of diameter 120mm

Area = 60mm*60mm*3.14 = 11304
11304/645.16 = 17.52 square inches 17.52/144 = 0.12SF

.12SF = 30CFM/FPM FPM = 30/0.12 = 250 FPM

FPM = 250

Conclusion: Area under case provides more area than a 120mm fan opening. This is too much like math class. I think it should work but hell I don't know.

[teejay]

Still an entirely theoretical discussion, but... I usually simply calculate the area to check whether an intake is restricted, since using the same volume displacement for both in- and outflowing speed calculations will yield the same conclusion as an area-comparison.

Following your calculations I add two facts: there are two 120mm fans in the case taking in air from underneath the case and the actual blade area of the fan is the part where the air flows through. This area is smaller than pi*r^2. With the simplifying assumption that each fan uses one opening (either front or back) the intake area for one fan becomes 0.078 SF which yields a speed of 384 FPM. For the fan area I take MikeC's figure, 87 square centimeter or 0.094 SF which gives a speed of 320 FPM. So, as stated before: this is a slightly restricted intake.

Or, like I said, you can compare areas: 87sq.cm for the fan versus 72 sq. cm (1.5 * 7.5 * (2.54)^2) for the intake which also tells you there is a bit of restriction. But I'll repeat again: this is purely theoretical, most cases offer only a fraction of this area for intake and work fine too. 1.5" should be adequate but if you want to have math on your side you could make it 2"

Btw, frankgehry, I do hope you see the fun in this type of discussion and take no offence... none is intended!

[frankgehry]

Oh no TJ. This is a lot of fun and I take no offense. We're just getting started too. Earlier, we were thinking about one fan, but now I agree that it would be best to start out with two or at least have the option of adding another one. Best - FG

[Gorsnak]

[*]De Sjelle has a good point; I have read several stories of peoples wooden cases cracking because of rigid construction;

I strongly suspect any cracking was due to wood that wasn't entirely dry when the case was built. Temp variations won't result in much expansion/contraction, but moisture content variations certainly do. Drying would be accelerated under the warm conditions with moving air, and could well cause cracking. What this suggests is that I should buy stock soon so it can sit somewhere warm and dry for a month or so before I start construction. Then if I use a good sealing finish to avoid picking moisture back up, it should be fine.

Thanks for the ideas so far. Keep'em coming.

I can certainly put a barrier over the psu. Over the top, and over front too, assuming a Tornado is used. I had initially planned to do just that, but rejected it because it complicates covering the entire door with my acoustical panel. I can work around that, though.

I don't think recessing the top fan is too likely to create a pocket of warm air if it's only in 1.5" (two 3/4" boards, plus the back, for a total depth from outside edge of 2.25"). This isn't as recessed as the psu is, and it'll probably be the greater noise source, but it is at the back.

I'm thinking it might be a good idea to modify the intake to just a big circle the size of a 120mm fan, though, for the purposes of possibly someday adding an intake fan. I'm not sure how necessary a filter might be, though it's something I have been thinking of. But I don't see that it would suck any more dust than any other box.

[teejay]

I strongly suspect any cracking was due to wood that wasn't entirely dry when the case was built.

You're the wood wizard!

I can certainly put a barrier over the psu. Over the top, and over front too, assuming a Tornado is used.

Yeah, that is what I meant. In this case, I would not use anything but a bottom-feeding PSU. Another thing that I just thought of: I've read somewhere that those PSU's can benefit noise-wise from placing the fan just outside the PSU enclosure, mounted in its intended holes only on the "wrong" side of the casing. This apparently reduces audible turbulence from nearby components. Since you're designing from scratch anyway, maybe this too is something you could account for in your dimensions. I'd love input from other members on this subject too as it is one of the mods I am planning for (or would that be considered a thread hijack? )

The need for filtering depends greatly on your surroundings. I agree with your conclusion, I don't think this setup will be more or less dusty then any other regular case.

[Tibors]

I put the 120mm fan from my AOpen PSU (simmilar to a Fortron Aurora) on the outside of the PSU casing. At the same time I removed the wire grill and replaced the fan screws with rubber sticks. It helped a bit, but the result is not spectacular. Still if you have the space to make your case 1" taller there is no reason not to do it. (Except for the loss of warranty of course.)

[De Sjelle]

Excuse me for boring you to death with the wood thingy but when you build a wooden box of that size with massive wooden panels attached together so that the wood can't move it will crack eventually.

*edit* Congrats with that fine desk you made.



I took the liberty to make some drawings to suggest how to make a wooden box in massive wood.
( Take care with pine wood; it has the tendency to move rather a lot. )

[Gorsnak]

I've been a bit preoccupied with other things, but I've gotten back to revising the design. I've become convinced that resonance is an issue. I discussed this with my boss, and he says that high end speakers use 13-ply birch with internal ribbing to avoid it. Higher density helps, as does the multi-ply construction, because the resonance of each ply will be different. However, using plywood wouldn't allow me to build it the way I want without exposed edges, and exposed plywood edges are ugly, not to mention there's no possiblity of any internal ribs. The other option is isolating everything that vibrates from the case, so that's the route I'll have to take.

I'm still not overly concerned about splitting, but I've changed things up a bit so that both sides will swing open (desirable in its own right), while the top, bottom, front, and back are single widths, so this shouldn't be a problem.

Some pictures. I ended up not putting anything over the psu, since I'm trying to keep the size down (it's sitting at 21" high, 10 7/8" wide, and 20 3/4" long) and that would add 3/4" to the height. A Tornado at ~150w output is only radiating ~40w of heat anyways, and most of that goes out the back. If need be, I can cover it with a bit of insulating tape.




Here's the bottom. I've blocked off the back to avoid any chance of the psu exhaust getting sucked back in, and opened up the sides. There's ~30 square inches open around the sides and front. The bottom intake is now set up for a possible future intake fan. I'll likely put a few more holes in the bottom as well.



The reverse side. One upright is inserted to fix the mobo tray to, and to stiffen things up now that the right side is a door rather than a structural part of the case.



All closed up, and with the finishing touches, and with front and left doors open.

[frankgehry]

G,

Nice refinements.

[MikeC]

Your design has evolved nicely.

Find ways to integrate elastic suspension for the HDDs and perhaps even the fans... tho the latter is not difficult to mechanically decouple using things like EAR fan mounts.

When you're done, I'd suggest you write a DIY article for SPCR.

[Gorsnak]

I was thinking at the least I'd take a bunch of pictures during construction and post them, but an article would be quite doable as well.

The hdd will be suspended. You may have noticed that it's just hanging in midair at the moment, but the plan is to extend a pair of dowels back from the front of the case over the hdd a bit, and then run shock cord between the dowels and the bottom providing spaces for two drives. Hanging them vertically should provide optimal cooling and airflow past them, and since the sides of the case swing open, is simpler construction-wise. The hdd and the fans are the easy ones. I think I can more or less set the psu on some soft rubber blocks. The optical drives and the mobo provide greater challenges. For the drives I'm thinking of cannibalizing an old drive cage, and screwing it into the top panel with rubber isolators between the cage and the case, and between the screws and the cage. Other ideas would be welcome, though. It's kind of tricky, since the drive faces have to sit rather stably in their little openings. For the mobo tray I have no ideas at the moment. Perhaps it would be easiest to mount it solidly, and then isolate the heatsink fan from the heatsink.

[MikeC]

I was thinking at the least I'd take a bunch of pictures during construction and post them, but an article would be quite doable as well.

Good.

I think I can more or less set the psu on some soft rubber blocks. The optical drives and the mobo provide greater challenges. For the drives I'm thinking of cannibalizing an old drive cage, and screwing it into the top panel with rubber isolators between the cage and the case, and between the screws and the cage. Other ideas would be welcome, though. It's kind of tricky, since the drive faces have to sit rather stably in their little openings. For the mobo tray I have no ideas at the moment. Perhaps it would be easiest to mount it solidly, and then isolate the heatsink fan from the heatsink.

Your PSU idea will work fine. You could even carve up a block of med density foam for it to sit within and then strap the thing down with elastic.

Hard mount the motherboard; anything else will cause issues at the I/O panel. Chances are, your CPU fan will be running slow enough so that vibration transfer will be neglegible.

If you wanted to work on isolating the optical drives, think blocks of foam, carved up so that the drive gets wedged in place. Sort of like this fan mount I devised for the PSU test rig:

[ronrem]

I built a subwoofer with a 12",2 x 10" and an 8" able to put out a lot of DEEP bass- I used particle board with a 1/4" veneered oak plywood skin glued on with constrution adhesive-the kind in red,yellow +black caulk tubes. As I had no good way to mitre,I did the corners with Oak L mouldings. finished with a Red Oak stain and a lot of Man-O War gloss spar varnish-looks sharp-no cabinet resonanse problems. Another thought,I'd add a little bottom clearance,maybe an inch,reverse the PSU fan to exhaust out the bottom,and have at least a 120mm exhaust on the bottom. On the back I'd attempt to do a housing for a good size air filter. My 86 Camry uses a rectangle shape that could work. You can use solid wood for your front case and door-which is what you mainly see. Some indirect path inflow from the front would help keep drives cool,that would be a semi maze of wood so air flows and sound is obstructed-put some padding/insulation on some surfaces to reduce echo effects. You will want your side door to have some absorbant,echo stopping liner

[ronrem]

I made a motherboard tray out of an aluminum tray,like used to carry plates of food on-75 cents,yardsale,an aluminum cookie sheet also could work. Check Goodwill or similar.

[darinw]

I've read a lot about wooden cases, and there is just one question that keeps me from building my dream machine...
Grounding.
What components in a typical system have to be case grounded--if any--and I mean other than through the ground in the power connector?
For example, does the metal hard drive case need to be directly grounded to the power supply case, as it would be in your typical metal chassis?
My fear is that if my CDROM or hard drive case is not grounded--i.e. it is mounted on rubber feet--then static electricity or something could build up. Does the ground plane on the motherboard need to be coupled to the power supply case?

[JanW]

Very good looking project you have there, Gorsnak! I'm curious to hear how it worked out.

A couple of random thoughts:

• I've seen big furniture built entirely of pine which doesn't seem to crack, move etc, and doors still close neatly after dozens of years. But in my personal experience of building a few pieces of furniture as a hobbyist I found this very difficult to achieve (well, I haven't been able to). So in view of the temperature changes a computer case is subject to, I'd second the suggestion to make the internal structure out of thick particle board or good quality plywood. I've used MDF to build speakers, and it's very sturdy, not likely to resonate, and won't move with changing humidity and temperature. The front seems to have two layers of wood already, so the inner one could be MDF, and you could do the same on the top. You'd just need to hide the MDF behind the front door with a thin layer of pine. Hardwood might work, too. Be sure any solid wood has been well dried when you buy it. Storing it at room temp for a month sounds like a good idea, but if it wasn't already reasonably dry before, it might crack.
• It looks like you have a lot of space in the lower front, inside the case. If you think you might want to add a filter later on, an opening of the size of the fan will be too small. But you could add an enclosure to the lower front, the height of the PSU and going from the front back up against the PSU. You would then move the 120mm-sized hole to the top of that box and have room for a large opening at the bottom of the case. The harddrive would just move up accordingly. The large opening could house a filter later on.
• Having the side-panels as doors, at least the one on the left side, seems like a good idea if you like to tinker with your box from time to time (who doesn't?). But I think it could be difficult to make the door fit neatly, close the box tightly, and avoid any resonances. I don't have any experience with this and can't help, but it strikes me as something that needs to be thought out carefully. I'd think twice about whether the right door is necessary, as closing that side will greatly add to the stability of the whole box. If you do close it, I'd again suggest MDF or plywood with a thinner layer of pine for looks.

[Gorsnak]

1) Wood doesn't expand or contract to any appreciable degree due to temp variations. The expansion, contraction, and general movement of wood is due to variations in moisture content nearly exclusively. Now, I can tell you that the humidity levels in Saskatchewan range between very dry in summer, to extremely dry in winter. I exaggerate only slightly. Apart from the initial drying of the wood, there won't be a great deal of variation here.

2) I am not sure at this point where people are expecting cracks to develop in this thing. Front, back, top, and sides are to be made from single widths the widest stock readily available, i.e., 1x12 (which is actually 3/4" x 10 7/8", but that's a different story). To the extent that they are going to change in size, they will tend to do so in unison (changes are almost exclusively in width - length doesn't change hardly at all), which won't put any significant strain on any individual piece. Crack-causing stress is most likely to occur where one has a longish chunk of wood with the grain running lengthwise firmly anchored to a panel or some such where the grain is running perpendicular to the longish chunk. In such cases, moisture level variation can result in the panel wanting to contract in width, but the lengthwise piece won't want to contract with it. Since the ends of the panel are fixed in place, something's got to give, and you end up with cracks somewhere in the middle. My desk is actually potentially susceptible to this, since I didn't do much to account for it. We're coming up on two years for it, and nary a sign of cracks yet, but it's possible that in the midst of a winter after a relatively humid summer something might happen in the future. Anyways, there are no such construction points in this design. There were in the initial drawing, with the right panel fixed, but in the current design, the only place where there's a joint with the grain running perpendicular is where the mobo backing is joined to the top and bottom. And if that board develops a crack, it just doesn't matter, as it's hidden from view.

I am reluctant to build an inner case from mdf or whatever and face it with pine because I don't know what I'd be gaining. I guess I could build a box from 1/2" mdf with open sides, and then face the top and front with pine and add the side doors (making doors with a pine panel fixed atop mdf is a good recipe for developing cracks in the pine, unless we're talking about a sheet of veneer (blech) or having the pine floating loosely atop the mdf (structurally no different than pine alone)), but to what end? It wouldn't be stronger - it would actually be weaker, as screws don't get nearly the bite in mdf that they do in real wood. It wouldn't be any less resonant, as mdf is prone to resonating as well. It would, I suppose, be a tiny bit less prone to cracking, assuming that I anchored the face pieces in such a way that they could float relative to the backing, but I just don't see where crack-inducing stresses are likely to build up on the top and front of my design to begin with.

3) Re: snug-fitting doors. This is an issue, but I think I have it under control. I'll be running a cleat along the inside of the top and bottom, so that there's 3/4" backing inside the door all the way around. This will be covered in some sort of thickish fabric. The right door will be closed by means of two posts passing through the framework at the front and anchored with wingnuts. (Note to self: draw that frame piece in so it doesn't get left off the cutting list.) In ordinary operation, it wouldn't be opened, and should be pretty solid. In combination with the mobo backing board, it should be plenty to keep the case as a whole solid. The left door will be held shut with some sort of cabinet hardware, likely the sort where the arrowhead-shaped thing on the door pushes between two springloaded rollers. I'll be looking to get a rather substantial set of such items. Snug fit over time should also not be too much of a problem. Size changes vertically will be negligible, as the grain will be vertical. The greatest expansion/contraction effects on the case, though, will be seen in the width of these doors. However, it should be possible to adjust the position at the hinges slightly if they become overly tight or loose.

I'm hoping to get the cutting list drawn up today yet, and pick up the lumber sometime this week so it can sit around and acclimate to the humidity of my apt. Then we'll just have to wait for work to be slow enough that I can take a few days off and head out to the farm (so that I can use all of Dad's power tools ).

[JanW]

{Good lesson about the properties of wood}

Ok, lesson learned Gorsnak. You obviously know more about this than I do. I've seen pine panels crack all on their own (nothing fixed to them), but they admittedly were a whole lot bigger than the pieces you're using, and cracks were probably due to drying them too fast in the first place. Good luck with your project!

[Gorsnak]

Ok, lesson learned Gorsnak. You obviously know more about this than I do. I've seen pine panels crack all on their own (nothing fixed to them), but they admittedly were a whole lot bigger than the pieces you're using, and cracks were probably due to drying them too fast in the first place. Good luck with your project!

Yeah, almost certainly it was a drying issue. Most cracks develop during the initial drying period which, due to corner-cutting by lumber companies, often isn't finished until well after the consumer has purchased the board.